Basic helpers and tasks for building a controller

🔵 This MR is based on !16 (closed) breakdown. These changes are tested in the broader context of !16 (closed).

⚠ This MR is based on !19 (merged), !18 (merged) and !17 (merged). Do not merge it before !19 (merged).

✅ This MR must be rebased after merging !19 (merged).

What does this MR do?

This change includes Task interface and a few implementations, including:

• ApplyObjects: Runs ApplyObject function on a list of Objects.
• Dereference: Loads Objects of type T that are referenced in a source Object of type S. For example all Secrets that are referenced in GitLab. It uses a Reference interface to locate the referenced Object.
• GetObjects: Returns a list of Objects of type T that are specified with in the list of qualified names.
• RenderTempaltes: Renders the specified templates with the given data.

Author's Checklist

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Ensure a release milestone is set.
• MR title and description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• MR has a green pipeline on GitLab.com.
• When ready for review, MR is labeled workflowready for review per the MR workflow.

Expected

• Test plan indicating conditions for success has been posted and passes.
• Documentation is created or updated.
• Tests are added.

Related issues

Related to #2 (closed)